According to Wired Science, NASA craft had to dodge orbital debris four times in 2008.  Given that on average NASA and the ISS need to avoid orbital debris once a year, this is a noticeable uptick in incidents.  This doesn’t count classified missions or the efforts of other spacefaring nations, so the number is likely higher.

Part of the problem comes from two recent incidents, a collision and a missile test by the Chinese.  Both events significantly increased the amount of debris in orbit.  As the Wired Science article indicates, this debris increase has already forced change in a Shuttle mission involving the Hubble Space Telescope and forced International Space Station personnel to take cover in a Soyuz capsule as protection against a possible collision.  While some of the testimony at the Congressional hearing on this issue held earlier this week seemed to downplay the issue, should China or other countries become regular spacegoers, or increase their satellite activity, the need to avoid debris will increase.  It might be wiser to establish some protocols for removing debris before it provokes an incident.